Electronic locks use an electrical servomechanism to reversibly block locking or unlocking. In some locks, the plunger of the solenoid functions as the bolt or latch of the lock. In other locks, the plunger is configured to reversibly prevent the movement of a separate bolt or latch. In either case, the plunger performs a linear movement or rotation under the influence of electromagnetic forces and elastic elements.
Electronic locks in general are widely known and used as locking mechanisms in doors, windows, boxes, cases, drawers, safes, padlocks, bicycle locks, etc. Some electronic locks have a keypad control panel near the door or on the door itself, which is used to input an entry code. Other types have magnetic card readers for input of the entry code, as used in hotels and some condominiums. Yet others have sophisticated receivers and may be operated remotely, for example door locks of cars.
There are attempts to combine the advantages of the electronic locks and the mechanical locks, especially when retrofitting existing doors with new electronic locks. US Pat. Application Publication 2001/0027671 discloses a system comprising electronic. cylinders and electronic keys. The electronic cylinder has no power supply but has a built-in microprocessor and memory chip and electric contacts in a recess accepting the key bit. The electronic key contains a battery to operate the cylinder, and a microprocessor with memory. The key serves also as a handle to turn the cylinder in the lock and to open the lock bolt.
WO 99/61728 discloses an electronic cylinder lock comprising an inner and an outer cylinder plug, a battery, a servo actuator, a control unit, and a mechanical clutch. The servo actuator and the clutch are disposed in the cylinder between the plugs, in a rotary cam engaged with the locking bolt. An electronic key for this lock is described in WO 97/48867. The coded signal is transmitted via electric contacts in the key bit and in a recess in the cylinder plugs. Normally, neither cylinder plug is engaged to the rotary cam. When a key is inserted in one of the plugs and the coded signal is recognized, the servo actuator operates the clutch and connects the plug to the rotary cam.
U.S. Pat. No. 6,411,195 discloses a data transmission system including a data transmitting device having a reciprocable impact head for delivering an encoded series of mechanical impacts to a first surface of an impact transmissive body such as a door, and a data receiving device having a sensitive microphone at a second surface of the impact transmissive body for picking up vibrations resulting from the series of impacts. The data transmission system is suitable for use in coded access systems.
U.S. Pat. No. 6,865,916 discloses a cylinder lock for use in a door lock, comprising an outer plug, an inner plug, a rotary cam adapted to move a deadbolt of the door lock, and a clutch adapted to engage for rotation the outer plug to the rotary cam. The cylinder lock further comprises an electronic blocking device (EBD) and a drive adapted to actuate the clutch upon an unblocking command from the EBD generated upon receiving therein an unblocking signal emitted from the outer side of the door, thereby enabling moving the deadbolt by rotation of the outer plug. The cylinder lock comprises an inner handle attached thereto at the inner side of the door, the EBD and the drive being entirely accommodated within the inner handle. The signal is emitted by an electronic key or panel and may be a mechanical vibration signal, a light signal, or a radio signal.
US Pat. Application Publication No. 2006/0179903 discloses a mechanism for an electromechanical lock. The mechanism comprises a shackle or strike moveable in a bore. A cam is rotatable between a first cam position in which movement of the shackle or strike in the bore is prevented and a second cam position in which movement of the shackle or strike in the bore is not prevented. A blocking pin is moveable between a first pin position in which rotation of the cam is prevented and a second position in which rotation of the cam is not prevented. A solenoid has a plunger having a stable extended position in which movement of the blocking pin is prevented and a stable retracted position in which movement of the blocking pin is not prevented.
While each of the above constructions has its advantages, it is desirable to avoid some deficiencies such as exposure to tampering or malevolent damage, etc.